In certain fuel systems, such as for vehicles, a pump is provided to move fuel through the system such as from the tank to the engine. A filter element may be provided downstream (on the pressure side) of the pump to protect downstream components. At start-up and during operation of the system, air can be pushed into the filter housing. It is desirable to vent the accumulated air in the housing to avoid the air being pushed through the element. The air can create erratic fuel delivery, and effect performance of the downstream components.
To allow the air to bleed slowly out of the housing as the housing is filled with fuel, a vent orifice may be provided in the upper part of the housing. By sizing the orifice appropriately, and by locating the orifice in the upper part of the housing, the orifice will essentially only allow air to vent out. Any loss of fuel is fairly insignificant and can be collected and directed with the air back to tank.